[logback-user] logback.xml not reloaded

Hi there, I would like to know if there is a way to debug why logback.xml configuration change cannot be reloaded by our application. It had been working correctly on our application for a long time, however I discover from a week ago that change at runtime is not applied. If i restart the application, the change is applied properly. configuration xml is using basic one using scan="true". I tried adding debug="true" but no information message apart from usual logback information message before application startup. The only change I can think of is we change Tomcat from 6.0.x to 7.0.56. We are using logback version 1.0.13. Any assistance is appreciated. Thanks Johanes